Breaker Breaker One Nine

steverkemp · 09-24-2018, 06:22 PM

My Cobra Classic CB on my 19 DX3 doesn’t pick up anything on channel 19 or otherwise. When I spoke with Greg at Dynamax he indicated that they commonly don’t work and that it may need to be tuned. I checked that the antenna is plugged in. Any ideas? Thanks!

CSWVK · 09-24-2018, 06:35 PM

hi, ours had a bad internal speaker when we received it. The speaker coil was open. I bought a replacement at fry's for about $5 and now its all good. It was a pain to get it out.

Scrapper · 09-24-2018, 06:54 PM

Quote:

Originally Posted by steverkemp

My Cobra Classic CB on my 19 DX3 doesn’t pick up anything on channel 19 or otherwise. When I spoke with Greg at Dynamax he indicated that they commonly don’t work and that it may need to be tuned. I checked that the antenna is plugged in. Any ideas? Thanks!

The tuning that Greg mentioned is done at the antenna or antenna cable. It requires a signal strength meter connected to the antenna input connection at the back of the radio, then the antenna lead connected to the meter. The antenna lead or whip is shortened by 1/8" at a time. With the right tools it is a fairly easy, but can be slightly time consuming. The length of the antenna lead from the radio to the tip of the whip needs to be adjusted to the wavelength of the signal. One thing you have to remember is if you tune it by cutting the whip is you can not replace what is cut off. The longer the whip the better the transmission/reception. I have found it is easier to adjust it by trimming the antenna lead. Some antennas have a setscrew at the whip base so you don't need to cut it, you loosen the setscrew and move the whip up or down to fine tune it. The signal strength meter is a must.

My best advise to give you is to go to a truck stop with a CB shop or an independent CB shop. They will test the radio and make short work of the tuning.

steverkemp · 09-24-2018, 09:18 PM

Thank you. Is there a rule about 2 ft of clearance around the antenna? I heard that from a Jeep guy and since I have a cab over bunk that would definitely be less than 2 foot as the antenna extends well above the cab of the chassis.

steverkemp · 09-24-2018, 09:19 PM

Quote:

Originally Posted by CSWVK

hi, ours had a bad internal speaker when we received it. The speaker coil was open. I bought a replacement at fry's for about $5 and now its all good. It was a pain to get it out.

Good to know. Did you have to do any tuning per se?

Scrapper · 09-25-2018, 12:06 AM

CB radios need what is called a ground plane. The fiberglass bodies and non-metal roofs of many RV's don't supply it but there are ways to work around it. The jeep guy was correct that you need space around the antenna base for that ground plane. Semi-truckers found a way to deal with it by mounting the antennas at the top of their large mirrors. For jeeps, there was a 102" whip antenna that reached up above the body quite a bit. I had one on my '75 CJ5 rag top. If I looped the tip of the antenna down and hooked it to the front so I park in the garage all transmission/reception was lost.

BobHanke · 09-25-2018, 01:35 PM

Scrapper got it right. The non-metalic bodies of most class-A rigs will not allow for use of a ground plane antenna. A CB shop mounted a short non-ground plane antenna on the pillar to left of windshield and found an adjustment switch for the power shade while the installation was going on. This is not a very effective setup but we can get info to help through traffic tieups and the National Weather Service side of our Cobra works great. Class-C's can do better but might find a mount that works between the hood and fender gets the clearance from the main body better. There are two mounts for this depending on if the hood meets on the top or side. Truckers with the conventional metal cabs run twins because the outside mirrors get the 8 foot (1/4 wave) separation that the setup needs for maximum range.

TheWolfPaq82 · 09-25-2018, 02:09 PM

Quote:

Originally Posted by Scrapper

The tuning that Greg mentioned is done at the antenna or antenna cable. It requires a signal strength meter connected to the antenna input connection at the back of the radio, then the antenna lead connected to the meter. The antenna lead or whip is shortened by 1/8" at a time. With the right tools it is a fairly easy, but can be slightly time consuming. The length of the antenna lead from the radio to the tip of the whip needs to be adjusted to the wavelength of the signal. One thing you have to remember is if you tune it by cutting the whip is you can not replace what is cut off. The longer the whip the better the transmission/reception. I have found it is easier to adjust it by trimming the antenna lead. Some antennas have a setscrew at the whip base so you don't need to cut it, you loosen the setscrew and move the whip up or down to fine tune it. The signal strength meter is a must.

My best advise to give you is to go to a truck stop with a CB shop or an independent CB shop. They will test the radio and make short work of the tuning.

The "SWR" needs to be set. Standing Wave Ratio.

rskeans · 09-25-2018, 02:56 PM

I never thought that our factory CB was working until I got stuck on the I-40 in Flagstaff. Then it came alive with the truckers advising where the problem was. It probably has very limited range.

Scrapper · 09-25-2018, 07:33 PM

Quote:

Originally Posted by TheWolfPaq82

The "SWR" needs to be set. Standing Wave Ratio.

The Standing Wave Ratio is what you are adjusting when you use the signal strength meter. You want to get maximum deflection of the meters needle. Cutting off of too much or too little of the antenna cable will cause the needle to drop. That is why I recommend cutting the cable and not the whip. I don't remember the exact measurements (may be wrong but I think it is 18 inches) but if you cut it and the needle starts dropping then you can cut off some more to bring the needle back up. It's been a long time since I installed a CB. Had them in 4 vehicles and a base station back in the 70's.

TitanMike · 09-25-2018, 10:35 PM

There is a relatively inexpensive work around for not having a tin roof that acts like a ground plane. Instead of using the more common 1/4 wave antenna that relies on a ground plane for "the other half" get a 5/8 wave antenna like a "Firestick". A lot of truckers use these mounted on the mirror bracket. Some use lots of wire wound around a fiberglass "stick" and may or may not have a "tuning stub" of coax at the base in addition to the regular feed coax.

Firesticks have been used for years with much success.

As for CB in general, lots of truckers just use Cell Phones to yak with their buddies.

Some even use FMRS radios.

I quit taking my CB along about 10 years ago. Got tired of listining to truck drivers yakking for hours on end from some other part of the country (skip). I figured I could look out my windshield and see what was going on as well as any report on the CB. Oh yeah, less profanity to listen to. Some truck drivers are able to make a whole paragraph out of the "F-Bomb".

FWIW, Waze is pretty good if you have cell coverage. Lots of people use it today and if there's an accident or other traffic hold up you can pretty well expect someone ahead will report it.

steverkemp · 09-26-2018, 12:43 AM

Quote:

Originally Posted by TitanMike

There is a relatively inexpensive work around for not having a tin roof that acts like a ground plane. Instead of using the more common 1/4 wave antenna that relies on a ground plane for "the other half" get a 5/8 wave antenna like a "Firestick". A lot of truckers use these mounted on the mirror bracket. Some use lots of wire wound around a fiberglass "stick" and may or may not have a "tuning stub" of coax at the base in addition to the regular feed coax.

Firesticks have been used for years with much success.

As for CB in general, lots of truckers just use Cell Phones to yak with their buddies.

Some even use FMRS radios.

I quit taking my CB along about 10 years ago. Got tired of listining to truck drivers yakking for hours on end from some other part of the country (skip). I figured I could look out my windshield and see what was going on as well as any report on the CB. Oh yeah, less profanity to listen to. Some truck drivers are able to make a whole paragraph out of the "F-Bomb".

FWIW, Waze is pretty good if you have cell coverage. Lots of people use it today and if there's an accident or other traffic hold up you can pretty well expect someone ahead will report it.

Sage advice

markb422 · 09-26-2018, 07:52 AM

Question on ground plane. I made a metal bracket that I attached to the top rail of the MH for my magnetic mount antenna. I am sure that the mounting screws go into the aluminum frame of the wall. It works good but I am curious if I ran a ground wire to the bracket from the chassis of the MH would it work even better.

bareftn · 09-26-2018, 09:17 AM

99% of truckers are not on 19 anymore

wanderingbob · 09-26-2018, 09:22 AM

Apparently the China tariff has put Cobra out of business , laid off 160 employees , 50 percent duty on electronics ! They are no longer shipping to truck stops .

The Renegade · 09-26-2018, 09:34 AM

I know you will figure out how to make this work Steve so keep us up to date. I just thought I needed to spend some time on mine tuning it but have been busy on other things right now. I would like for it to work rather then just being an ornament hanging from the cab. Plus the grandson is not gonna leave me alone till it works.

TheWolfPaq82 · 09-26-2018, 09:39 AM

Quote:

Originally Posted by wanderingbob

Apparently the China tariff has put Cobra out of business , laid off 160 employees , 50 percent duty on electronics ! They are no longer shipping to truck stops .

Wasn't any Tariff that caused that. The CB industry has been on a slow death for 10 or more years now.

TheWolfPaq82 · 09-26-2018, 09:43 AM

Quote:

Originally Posted by Scrapper

The Standing Wave Ratio is what you are adjusting when you use the signal strength meter. You want to get maximum deflection of the meters needle. Cutting off of too much or too little of the antenna cable will cause the needle to drop. That is why I recommend cutting the cable and not the whip. I don't remember the exact measurements (may be wrong but I think it is 18 inches) but if you cut it and the needle starts dropping then you can cut off some more to bring the needle back up. It's been a long time since I installed a CB. Had them in 4 vehicles and a base station back in the 70's.

I never cut the coax. I always adjusted the "Metal" whips by trimming the end and some even had set-screws so you could move the whip up and down in the base. Goal was to have the "Lowest" possible SWR reading you could achieve. I always set below 1.5 and never settled for anything else.

hook47 · 09-26-2018, 10:34 AM

Mine doesn't appear to work either. Few months ago had Freightliner check it out and he could talk to another truck 50 ft away. Not real useful. What kind of OEM antenna is installed? Familiar with Firestick antennas from long ago. If I swap out antennas which Firestick do I get? Thanks.

houstonstroker · 10-01-2018, 10:03 AM

Mine did not work either and after taking the cubby apart, I found that the coax was not connected to the radio. This is a Freightliner installed dual purpose antenna AM/FM and CB. After making the connection and testing SWR it was not a great antenna.

I found the Freightliner bracket that the factory uses and installed a Firestik no ground plane antenna on the passenger side. Mine works perfectly. We usually travel with a group and the CB radios for us are useful.

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